Magnetic pulley



March 4, 1952 w. c. POTTHOFF MAGNETIC PULLEY 2 SHEETS-SHEET 1 Filed NOV. 18, 1946 BY LulLunm c. DOTTHORF HTTORNBVS Patented Mar. 4, 1952 UNITED STATES PATENT OFFICE 1 Claim. (Cl. 209-219) This invention relates to magnetic pulleys or roll type separators, particularly to means of that type that use permanent magnets for their attracting and holding power.

Heretofore, many types of magnetic pulleys L) have been provided for a variety of uses but subtudinally extending spacer bars, and longitustantially all of such pulleys have been powered dinally extending magnetic-conductive bars seby electro-magnets. In many instances, electrocured to the drum member and being positioned magnets are unsuitable due to the difiiculties in between the spacer bars; and a plurality of cirproviding direct current power for their operl cumferentially extending permanent magnets ation, which power may require a motor generator removably secured at their ends to the magneticor a rectifier circuit in conjunction with the conductive bars with circumferentially adjacent pulley. Then too, such circuits have relatively poles being of opposite charge. high operational and maintenance costs and are Reference now is made to the accompanying difficult to insulate. The D. C. energization curl drawings, wherein: rent for electro-magnets also presents a fire Fig. 1 is longitudinal section, partly in elevahazard due to the arcing and sparking of such tion, taken on line l-l of Fig. 2 of a magnetic current in going through contacts and switches pulley embodying the principles of my invention; and such magnets decrease in efliciency, as their Fig. 2 is a transverse section, partly in elevatemperatures rise due to either external or intion, taken on line 22 of Fig. l; ternal causes. Furthermore, some materials, such Fig. 3 is an elevation, partly in section, of a as certain plastics, are deleteriously affected by modification of a magnet of the invention; and heat so that they cannot be used in association Fig. 4 is a vertical section of a modified belt with electro-magnetic pulleys in many instances. retainer disc of the invention.

Several types of permanent magnet type mag- Referring in detail to the pulley of the innetic pulleys have been'proposed in the past but 'vention, a pair of disc-like end members [0 are such magnets have not provided the desired shown which have a plurality of uniformly cirstrength magnetic field, or have been too costly. cumferentially-spaced longitudinally-extending The general object of this invention is to avoid spacer bars ll, secured to inwardly directed the foregoing and other disadvantages of and flanges I2 of the end members by bolts 13. The objections to known types of magnetic pulleys and spacer bars II, and the ends Ill are made from to provide a permanent magnet powered pulley a suitable non-magnetic material, such as aluor separator which has a strong attracting and minum, and the bars Il may be recessed on their holding field that is of substantially uniform inner surfaces at M to reduce their Weight and strength over the length of a relatively large cost. The ends in may have apertured center pulley. bosses [5 through which a mounting shaft 16 Another object of the invention is to provide extends. Then to render the field and strength a magnetic pulley with a plurality of circumof the pulley uniform over its length, as will be ferentially spaced permanent magnets adapted hereinafter explained, a plurality of steel bars to provide a maximum efficiency of action. I! are secured to and extend between the flanges Another object of the invention is to provide 12 of the ends I 0 in uniformly spaced circuma low installation cost, low weight, reliable magferential positions so as to close the gaps benetic pulley of sturdy construction. tween the spacer bars H and form a drum A further object of the invention is to provide therewith. a magnetic pulley having low operation and A primary feature of the invention is the use maintenance costs butwhich is of substantially of three relatively wide, broadly curved permaconstant strength for an extended period. nent magnets 18 around the circumference of the Another object of the invention is to provide a pulley to energize same. The poles or ends of magnetic pulley which has uniform fields therein the magnets 18 are secured by screws It to the at local portions thereof. bars I! with the individual magnets bridging Yet another object of the invention is to proover a spacer bar H. The magnets 18 are arvide a pulley or separator roll of such construcranged to form, in effect, annular sections; in the tion or assembly as to be easily and inexpensively pulley and I prefer to provide a plurality of such magnetized. annular sectional arrangements of the magnets T foregoing. and other o j ts and dv nspaced transversely along the pulley without, of

tages of the invention, which will be made apparent as the specification proceeds, are achieved by the provision of a magnetic pulley comprising, generally speaking, a drum member including end discs and circumferentially spaced, longicourse, interfering with or changing the integral construction of the pulley. Fig. 2 brings out that the adjacent poles of the magnets 18 are oppositely charged and also that the poles are evenly spaced around the circumference of the pulley. Of course, similar magnets of the pulley in different lateral portions thereof are similarly positioned and bridge over the same spacer bars H. A surprising element of the pulley of the invention is that a large amount of What otherwise would be the stray magnetic lines, or leakage of the magnets, is put to use by. the special shapes and spacing of the magnets. Taking a reading of the strength of the field one-half way between the poles of the magnets to be 100, by assembling them as disclosed herein, a field with a measurement of 75 is obtained between the poles of a given magnet and a field with a strength of 75 is likewise obtained between the adjacent poles of adjacent magnets, or a total useful field of 150 is obtained where a field of only 100 existed before.

The fields set up around the pulley, due to the special shapes and numbers of magnets used, define strong attracting forces while combining therewith good holding power. or, in other ,words, the. fields of the pulley extend out from its surface several inches while they also follow closely around its surface. In this connection, the bars II are not only spacer bars but they also form insulator bars in one sense since aluminum', or other non-magnetic material from which they are made, has a low premeability. Use of threemagnets of the wide, shallow type, as shown, or even substantially straight magnets, avoids excessive leakage of the magnets field from it between its poles. Also, the chordal relationship of the magnets poles permits only a minimum fieldloss due to its path being in a straight line through a spacer bar (and inside the periphery of the pulley) from one poleto another.

In order to reenforce the pulley on some wide models thereof, a plurality of hoop bars 20 are secured to and bridge between the spacer bars II and the steel bars I! on the radially inner surfaces thereof. The bars 20 are secured in place by screws 2| that extend through the bars I l and I! from the outer surface thereof to position the hoop bars 20. Ordinarily, the bars end at themiddle of the bars l! with one bar 20 bridging over one spacer bar and being secured to the adjacent steel bars. A plurality of the bars 20 arepositioned in slightly circumferentially spaced endto end relation to form a reenforcing hoop intermediate the end members l0.

spaced laterally thereof intermediate the annular sections formed by the magnets. The hoop bars 20 preferably are formed of a non-magnetic material, such as aluminum. In some instances, it may even be desirable to use a reenforcing disc of suitable construction in place of the hoop bars 20. v I

The magnetic pulley is provided with nonmagnetic discs 22 that are secured to and extend radially beyond the end members In by screws 23. The discs 22 ,serve to retain the pulley in engagement with a belt passing therearound and they have inwardly directed flanges 24 formed at their radially outer portions. Such flanges 24 fit over the ends of the spacer bars ll and steel A plurality of such hoops may be formed in the pulley, being is found the method of assembly and magnetization of the pulley of the invention so that the desired uniform field is obtained. To this end, the magnets, which are made from a conventional magnetizable material adapted to retain its magnetization, such as one of the Alnico alloys, which alloys comprise aluminum, nickel, cobalt and iron, are assembled in pulley sections prior to their complete magnetization. Alnico, has, for example, been found to provide good magnetic action without being of excess cost. These magnets are first magnetized by being exposed to a high strength electric field and then they are secured to the steel bars I! and again exposed to a suitable high strength field in order to produce the desired polarity and field strength in the magnets and their associated means. It seems that the magnets l8 lose a portion of their charge when they are attached to the bars I! but this charge is replaced and the bars are likewise charged by the exposure of the subassembly to the magnetic field. These bars I1 retain their charge, which is distributed uniformly along their length, as long as they are secured to the magnets l8.

The pulley of the invention may be secured to the shaft I6 by a key 21 that engages with one of the bosses l5 of an end [0. Screws 28 also may extend radially through the bosses IE to aid in securing the pulley to the shaft.

From the foregoing, it will be seen that a compact, strongly-constructed magnetic pulley has been provided by the invention. The pulley will retain its energization over a long period of time and hence will require little or no maintenance and will entail no operating costs for enegization current. The pulley can be journalled in any conventional bearings or housings and ordinarily it will be used with a belt extending around it and on which the material to be separated will be carried. However, it is possible to use the pulleys as a separator roll placed above the material to be cleaned or separated, or the pulley might even have the material passing. directly over its surface. Fig. 2 brings out that the radially outer surfaces of the spacer and steel bars are arcuate and that they blend to define a circle. This, figure also shows that the magnets are so formed and positioned as to leave the center of the pulley open for a mounting shaft.

Fig. 3 shows a modified type of anchoring means for the permanent magnets of the pulley which may be desirable in some instances. A magnet 30 is provided-with a cord out hole 3| whichhas a tapped steel or other suitable metal sleeve 32 positioned therein for engagement with a screw to secure the magnet in position. Lead or other filler metal 33 is placed around the sleeve 32 to secure it to the magnet. Fig. 3 shows that the base of the sleeve 32 is larger than the top of the sleeve to aid in retaining it in engagement with the magnet. V V V Fig. 4 shows a modification of the tapered pulley retaining disc 22 wherein a disc M is provided for use in place of the disc 22. The disc 4| has an axially outwardly overhanging flange 42 which tapers radially inwardly, as shown, to retain any belt around the pulley in association with it. Holes 43 are provided in the disc 4|; to receive securing meansfor positioning the disc on a pulley, which disc is so positioned that the laterally inner corner of the outer surface of the flange is flush with the pulley P, as indicated in Fig. 4.

While I have shownand described in detail several embodiments of my invention, it will be realized that I am not limited thereto or thereby and that the scope of the invention is defined solely'by the appended claim.

I claim:

A magnetic pulley comprising a shaft, a pair of spaced non-magnetic end members secured to the shaft, a plurality of bars secured to and extending between the end members, said bars being circumferentially spaced and abutting along the longitudinal edges thereof in side-byside relationship, the outer surface of said bars providing a continuous cylindrical surface extending between the end members, said bars being alternately of magnetic and non-magnetic material, a plurality of permanent magnets, opposite poles of the magnets being secured to the inner surfaces of the bars of magnetic material in circumferentially spaced relationship whereby alternate magnetic bars are of opposite magnetic polarity, and non-magnetic reinforcing bars secured to and extending between adjacent bars on the inner surfaces thereof, said reinforcing bars providing a hoop-like structure tying the bars together intermediate the end members.

WILLIAM C. POTTHOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 69,128 Righter Sept. 24, 1867 148,517 Smith Mar. 10, 1874 336,402 Fisher Feb. 16, 1886 446,767 Buchanan Feb. 17, 1891 451,370 Conkling Apr. 28, 1891 1,243,697 Bram Oct. 23, 1917 1,484,619 Blake Feb. 26, 1924 1,685,498 McCullough Sept. 25, 1928 2,188,091 Baerman Jan. 23, 1940 2,222,768 Gruender Nov. 26, 1940 2,466,839 Caldwell Apr. 12, 1949 FOREIGN PATENTS Number Country Date 401,301 Great Britain Nov. 6, 1933 607 Great Britain of 1880 nois, designated Bulletin 151A, Coolant Separators for Honing and Grinding Machines," published in 1944, February 23, 1945. 

